1. Field of the Invention
The present invention relates to a conductive pattern board and a method for producing the board which is preferably applied to a minute circuit board used for electronic devices such as a bar code display device or a fluorescent dot array device.
The present invention also relates to a conductive pattern connector comprising an insulative member on which conductive patterns are formed and a method for connecting the patterns.
The present invention further elates to an anisotropic conductive film for connecting conductive patterns with each other formed on an insulation member and a method for connecting the patterns.
2. Description of the Related Art
A conductive pattern board comprises an electric insulation member such as a glass substrate on which conductive patterns made from a conductive material such as Al, ITO or Ni are formed. Instead of the glass substrate, the insulation member may be composed of a ceramic member or a glass epoxy member on which conductive patterns made from Cu or Ni are formed. The materials and the patterning mode or layout of the patterns are determined according to the purpose and functional requirements of the pattern board device. Such conductive patterns are formed with a minute thin gap having a very narrow width interposed therebetween.
It has been required to obtain a pattern board device having a high integrated and high density minute pattern structure with high reliability in function. The minute patterns have become thinner according to progress in photolithography techniques.
However, the thinner the patterns are, the more possibility of problems of short circuit and leakage are involved, which causes a reduction in the functional reliability of the device.
Japanese Patent Application Laying Open (KOKAI) No. 58-108864 discloses a structure for connecting the patterns formed on an insulation member of the pattern board. The structure comprises a wire to connect two patterns on the board by a wire-bonding method, one pattern comprising a light emitting circuit segment, for example, and the other pattern comprising a driving circuit to be connected to the segment. The structure makes it possible to realize a small module unit.
However, after a long time of use when a part of the unit becomes unusable or the device malfunctions, the whole of the unit has to be exchanged.
Another structure for connecting the two patterns is such that an anisotropic conductive film is disposed between a connecting portion of one pattern (light emitting circuit segment, for example) and another connecting portion of the other pattern (driving circuit, for example) so that the connecting portions are electrically connected together in a state that the pattern connecting portions are arranged in a compressed air or gas. In accordance with this structure, it becomes possible to exchange only one of the patterns which has become defective after a long time of use, instead of exchanging the whole structure.
However, when the pressure of the compressed air or gas is excessively strong, the patterns and/or insulation member are damaged and cracks are generated therein. On the other hand, when the pressure is weak, the patterns are not reliably connected together.
Besides, the reliability of the connection between the patterns is further reduced when the anisotropic film is dislocated.
The anisotropic film comprises an insulation rubber as a basic material thereof. The film is subjected to a compressed atmosphere for a long time, which impairs the resiliency and flexibility of the rubber. Therefore, after a defective pattern is exchanged for a normal one, when the film is recompressed, the film does not reliably connect the patterns.